How Bradley Cooper transformed his body for 'American Sniper'

Actor gained 40 pounds of muscle in an effort to accurately portray the late Navy SEAL Chris Kyle.

Cooper had to seriously change his body to bulk up for the grueling role and pass for a Navy SEAL. (Photo: American Sniper)

With the first trailer for director Clint Eastwood's next drama "American Sniper" now online, we finally have our first look at Bradley Cooper as the elite Navy SEAL sniper Chris Kyle. As I mentioned earlier this year, Cooper completely threw himself into the role in an effort to not only portray the physicality of Kyle, but also honor his memory. The 38-year-old was tragically killed in 2013 after an incident involving another war veteran at a Texas shooting range.

"Thank God I got to talk to him once on the phone,'' Cooper told USA Today. "It was a very quick conversation. But I did tell him how serious I was about making this movie. And he should just know that whatever fears he had about Hollywood, to just put them aside and trust me. That I was going to do everything I could to tell this story."

"American Sniper" is based on Kyle's 2012 best-selling memoir of the same name which recounts how he became the most lethal sniper in American military history. To date, the SEALs have confirmed 160 kills out of Kyle's 255 claimed kills.

To prepare for the role, Cooper hit the gym and dramatically increased his daily caloric intake, embracing an eating regimen similar to those followed by Henry Cavill, Hugh Jackman and Ben Affleck.

"It was pretty brutal," Cooper told Entertainment Tonight earlier this summer. "I gained about 40 pounds. I'm about 20 down from that now. I ate 5,000 calories a day and doing whatever I could to pay homage to [Kyle]."

In addition to diet and exercise, Cooper also trained with Navy SEALs (including Kyle's former sniper partner Kevin "Dauber" Lacz) using live ammo in three types of rifles. One of the most intense moments, he recounted, came from looking through the scope for the first time and experiencing the gravity of Kyle's position.

"Even though it was actors through the scope, they were human beings," the 39-year-old said. "It was a whole other deal. I remember getting a chill through my body realizing what he had to do."

Check out the trailer for "American Sniper" below. The movie is slated for release early next year.